1. Field of the Invention
The present invention relates to a particle trapping-apparatus for removing particles including carbon particles as a main component thereof from the exhaust gas exhausted from an internal combustion engine, or more in particular to a method and an apparatus for detecting the degree of clogging of a particle-trapping-member including a filter member disposed in the exhaust gas passage of an internal combustion engine.
In an exhaust gas purifying-apparatus of a diesel internal combustion engine having a particle-trapping-member of a filter disposed in the exhaust gas passage, carbon particles staying in the trapping member cause the jamming thereof so that the back pressure is increased for a reduced engine output while at the same time deteriorating the fuel efficiency. It is thus necessary to detect the degree of clogging of the trapping member, namely, the quantity of the particles staying in the trapping member and to remove the clogging of the trapping member by burning the carbon particles staying in the trapping member at appropriate timing to regenerate the trapping member.
2. Description of the Prior Art
In conventional apparatuses, the timing of regeneration of the trapping member is determined in such a manner that a regeneration is conducted when the accumulated number of revolutions of the engine or the accumulated distance coverage from the preceding regeneration of the trapping member reaches a predetermined value.
The concentration of carbon particles in the exhaust gas varies with the operating conditions such as torque or engine speed by as much as more than five times. Therefore, if the timing of regeneration is set to a small number of accumulated engine revolutions or accumulated distance coverage, regeneration is often conducted undesirably before a considerable amount of carbon particles have not yet stayed in the trapping member. This results in frequent unnecessary regenerations, which in turn causes the deterioration of fuel efficiency and the driving feeling at the same time.
If the regeneration timing is set to an excessive number of accumulated engine revolutions or accumulated distance coverage, on the other hand, an excessive amount of carbon particles often come to stay in the trapping member, with the result that the back pressure is increased for a great reduction in the engine output, which also causes the deterioration of fuel efficiency and driving feeling at the same time. It is thus necessary to regenerate the trapping member at an appropriate timing by measuring the degree of clogging in the trapping member as accurately as practicable.
The degree of clogging of the trapping member is determined by the difference between the pressures before and after the trapping member. Since the internal combustion engine is used under various operating conditions and the difference between the pressures before and after the trapping member depend on a large measure the operating conditions for the same degree of clogging, however, it is impossible to determine the degree of clogging of the trapping member exactly by simply measuring the difference between the pressures before and after the trapping member.